Antennas have recently been designed in consideration of design of portable wireless devices. For this reason, antennas have been designed to be built-in. Further, progress has been made in reducing the sizes of the portable wireless devices, and thus sizes of the built-in antennas are also required to be reduced. Furthermore, such portable wireless devices are mounted with devices having various functions to meet user needs. For this reason, space for the built-in antenna tends to be increasingly reduced.
In such situations, slide type portable wireless phones, the housing of which is changed in length when opened/closed, have been provided, such as those disclosed in Patent Documents 1 and 2.
A slide type portable phone device disclosed in Patent Document 1 includes a built-in antenna in a lower housing for performing reception. Further, this portable phone device includes a parasitic element, in which one end thereof is grounded, on an upper ground plane in an upper housing that is provided to freely slide relative to the lower housing. This portable phone device is configured to resonate the parasitic element with the built-in antenna at a position at which the parasitic element and the built-in antenna are opposite and adjacent to each other, and to improve radiation power efficiency.
Further, a portable communication device disclosed in Patent Document 2 is provided with a parasitic element (resonant element), which is adjacent to an antenna element (driven element), at an antenna holder in a housing. This portable communication device is configured to switch connection and disconnection between the parasitic element and a substrate ground (ground conductor) to control polarization, and to seek to improve gains during data communication and during call service.